P=zeros(400,400,'uint8');
Q(:,:,1)=P;
Q(:,:,2)=P;
Q(:,:,3)=P;
for ii = 1:5
Q([1+80*(ii-1):80*ii],[1+80*(ii-1):80*ii], 1)=255;
end
image(Q);
%bonus: modify to have the colors change as ii changes